DNA vaccine, We constructed a baculovirus transfer vector pFastBac™Dual-derived DNA vaccine vector pFastBac-FA-VP6-ph-VP6 in which one gene was controlled by the baculovirus polyhedron (Ph) promoter, and another -actin promoter of grass carp, at the downstream of the baculovirus p10 promoter. Grass carp (weight 60−120 g, length 14−20 cm) were injected with 10, 30, or 60 μg of the vaccine vector, the negative control group was inject with 30 μg of pFastBac™Dual, and the unvaccinated control group was injected with 0.4 mL of sterile water. We then analyzed the pattern of expression in vaccinated fish using RT-PCR, measured antibody titers in the blood by indirect agglutination at 14, 21, 28, 49, and 70 d post-vaccination and evaluated immune efficacy by challenging GCRV at 21 d post-vaccination. The specific antibodies were detected in all vaccinated groups, and its levels peaked at 28^th day after immunization. The mortalities were 0, 0, and 5% in the vaccinated groups injected with 10, 30, and 60 μg of DNA vaccine, and 30 % and 100% in the negative control group and the unvaccinated control group, respectively. Our results suggest that the DNA vaccine had strongly immunoprotective efficacy against GCRV.